An electrode catalyst layer is formed on a surface of a conductive electrode substrate by a thermal decomposition method in the following electrodes: for example, an anode and a cathode for generating chlorine such as brine electrolysis; an anode and a cathode for generating oxygen such as copper foil preparation, metal winning, and metallic plating; and an anode and a cathode used for industrial electrolysis such as water electrolysis, and water treatment. An example of a substrate used for the aforementioned electrodes includes a rectangular plate-like electrode substrate such as an expanded metal mesh electrode substrate, and a plain weave mesh electrode substrate in which metal wires are woven in a meshed pattern.
In general, when an electrode surface having an electrode catalyst layer is prepared by the thermal decomposition method on a surface of an expanded metal mesh electrode substrate or a plain weave mesh electrode substrate, the electrode substrate is usually subjected to pretreatment, coating, firing, and post-treatment. Each of the treatments is performed while the electrode substrate is suspended by a suspension jig. In this case, a suspension hole may be provided to the substrate, or a small piece having a suspension hole may be welded to the electrode substrate. A claw portion of the jig is hooked on the suspension hole. Alternatively, the jig and the suspension hole may be fixed with a wire. Accordingly, the electrode substrate is attached to the suspension jig and the electrode substrate is in a suspended state.
However, such a plate-like electrode substrate has very low rigidity. In a case where the substrate and the jig are formed of different materials, they are different in coefficient of thermal expansion. Therefore, in the aforementioned conventional methods for suspending an electrode substrate, the substrate maybe bent, or wrinkles and creases may remain on the substrate during electrode manufacturing operations such as pretreatment, coating, and firing so that it is difficult to maintain final flatness and surface quality of an electrode as a product. There is another problem that the suspension hole may be deformed or broken, which causes a fall and damage of the electrode during the operations.
In order to solve the aforementioned problems, the present applicant has proposed a novel method for suspending a mesh electrode substrate (Patent Literature 1). In the method disclosed in Patent Literature 1, a unique jig is used. This jig includes two plates disposed in parallel and apart from each other so as to form a gap having a predetermined width between the two plates. In this method, upper and lower ends of the mesh electrode substrate are bent alternately, and the ends are processed so as to have a zigzag shape, and these bent portions are inserted into the gap of the jig. Accordingly, the electrode substrate is suspended as being supported by the jig. Such a structure makes it possible to attach the electrode substrate to the jig with good workability, and what is more, it is possible to disperse a suspension load to the entire width of the electrode substrate when the electrode substrate is suspended. Furthermore, since the substrate is not restrained, it is possible to suppress thermal deformation and wrinkles of the substrate generated during firing.